Production method of offset-shaped fins, fins, and method and apparatus for changing pitch of fins

ABSTRACT

An offset-shaped fin  4  can be continuously processed by roll molding by a method involving a first step of bending a flat sheet-like material  40 A into a concavo-convex shape by a pair of first rollers  5, 5 ′ to form a corrugate sheet  40 B; a second step of cutting slopes of the concavo-convex ridges of the corrugate sheet by a pair of second rollers; and a third step of bending the offset portion, offset and cut in the second step, by a pair of third rollers. A pitch-changing method of offset-shaped fins involves a step of supplying offset-shaped fins between at least one pair of pitch-changing rollers rotating while meshing with the other so that at least one pair of pitch-changing rollers clamp the offset-shaped fins between them, allow them to pass through said pitch-changing rollers and change their pitch.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a production method for producing offset-shaped fins, that are acquired by offsetting a corrugation shape of corrugate fins by roller molding, the offset-shaped fins produced by this production method, and a method, and an apparatus for the method, for changing the pitch of the offset-shaped fins that are produced in advance by roll molding, etc, particularly those which are used for inner fins of an oil cooler for a radiator, by increasing or decreasing the pitch to a desired pitch to be actually used.

2. Description of the Related Art

A stacked type heat exchanger that is produced by alternately stacking a plurality of conduit lines and corrugated fins (outer fins) to form a heat exchange core and causes heat exchange between a heat exchange fluid flowing inside the conduit lines and a heat exchange fluid flowing outside the conduit lines is well known. To improve heat transfer efficiency and performance of the heat exchanger in this case, it has been customary to arrange not only outer fins outside the conduit lines but also inner fins inside the conduit lines. Corrugated fins are sometimes used as inner fins in the same way as the outer fins but in this case, the corrugated fins merely increase the heat transfer area and the flow of the fluid inside the conduit lines is likely to become a laminar flow. Therefore, an improvement in heat transfer efficiency cannot be expected. To solve the problem, the construction shown in FIG. 2 is known. It is also known to use, as the inner fins, offset fins having a construction in which a plurality of concavo-convex ridges so shaped as to alternately repeat concavo-convex ridges are juxtaposed (corrugation shape) and the positions of the adjacent concavo-convex ridges are offset in the extending direction of the concavo-convex ridges. Consequently, because the heat exchange fluid flowing inside the conduit line flows while repeatedly branching and combining, the flow of the fluid changes to a turbulent flow and heat exchange efficiency can be further improved.

Such offset-shaped fins can be processed by a complicated mold mechanism such as a blank holder in press molding and have therefore been produced in the past by intermittent press working shown in FIG. 8. To reduce a processing cost and an installation area, there has been a demand in recent years for producing a complicated shape, such as an overhang that has been produced by press of intermittent working, by the roll molding shown in FIG. 9.

In the offset-shaped fins used for heat exchangers, etc, however, adjacent crests and adjacent troughs of adjacent concavo-convex ridges connect to one another in a relatively long area (about a half of the crest or trough). For this reason, each concavo-convex ridge can be formed only by press machining and roll molding, capable of continuous bending, basically cannot be applied to this shape. When the concavo-convex ridge is formed by roll molding, the portion at which the adjacent crests or troughs connect to one another is pulled back and forth in the direction of the concavo-convex ridge extending and thus undergoes deformation. Another problem is that the material damages the rollers. Therefore, it has been ordinary knowledge that roll molding is difficult to practice.

A method that solves this problem and forms an offset-shaped fin by roll molding is known from Japanese Unexamined Patent Publication No. 2001-221588. The production method of the offset-shaped fins includes a first rolling step (FIG. 10A), as shown in FIGS. 10A to 10C, in which first working rolls R1 conduct cutting and bending of an offset portion to form an intermediate work plate C1 having zigzag ridges having a triangular sectional shape from a flat plate C, and a second step (see Fig. 10B) in which second working rolls R2 serially apply bending (offset molding) at the connection positions of the zigzag ridges of the intermediate work plate C1, and fins C2 having concavo-convex ridges having predetermined trapezoidal sectional shapes are continuously processed in a predetermined form.

However, the system of Japanese Unexamined Patent Publication No. 2001-221588 in which the offset portion is bent into the trapezoidal shape after processing by applying cutting and bending is limited to the case where the length T of the coupling portion A with the adjacent convex portion offset is smaller than the thickness t of the material as shown in Fig. 1OC. In addition, penetrating the material into the rollers and breakage at the coupling portion A may occur because the cut amount is large and the coupling portion A undergoes large deformation during the subsequent bending work (slope portion → flat portion). Thus, stable processing cannot be expected.

From the aspect of the reduction of the production cost and the installation area, there are many cases in recent years where products which have a complicated shape and have been produced in the past by press of intermittent working are produced by continuous working by roll molding. Particularly when offset-shaped fins, used for heat exchangers, etc, are roll molded, the tooth shape is not established if the pitch fin is too short because the inclination of the crest portion of the fin becomes too acute. Therefore, the working involving the steps of first processing fins having an offset shape of fin having a predetermined pitch length by roll molding and then reducing the pitch length again to the short fin pitch or increasing the pitch length to the long fin pitch, on the contrary. Furthermore, when a punching step is employed after the change of the fin pitch, suppression of variance of the fin pitch per crest is extremely important because the fin is put into a punching mold.

Japanese Unexamined Patent Publication No. 6-63650 or 2002-254113 discloses a technology for reducing or expanding the fin pitch by means of the differences of friction and the number of revolutions of a plurality of sets of rollers. Each of these references can suppress the variance of the mean fin pitch per unit length but cannot suppress the variance of the fin pitch per crest.

Japanese Unexamined Patent Publication No. 2004-001026 discloses a technology for reducing or expanding the pitch by using a worm gear. Because the contact between the gear and the fin is a point contact, the technology is suitable for a corrugate fin having a small width, but cannot be easily applied to the offset-shaped fin having a large width.

When the fin pitch of the inner fins for a radiator, that have been produced in advance by roll molding, etc, is changed to a desired pitch at the time of the practical use as described above, the prior art technology involves the problem that offset-shaped fins having a large width cannot be reliably changed to the desired fin pitch while minimizing the variance of the fin pitch per crest.

SUMMARY OF THE INVENTION

In view of the problems described above, it is a first object of the present invention to provide a production method of offset-shaped fins having an offset shape by continuous roll molding without penetrating and breakage of a material, and the offset-shaped fins produced by this production method.

It is a second object of the invention to provide a pitch changing method, and a pitch changing apparatus, that can reliably reduce or expand a pitch of wide offset-shaped fins produced in advance by roll molding, etc, to a desired pitch, and can minimize variance of the fin pitch per crest.

According to one aspect of the present invention, there is provided a production method of offset-shaped fins including a first step of bending a flat sheet-like material 40A into a concavo-convex shape by a pair of first rollers 5 and 5′ having concavo-convex ridges 51 and 51′ formed on the surface thereof to form a corrugate sheet 40B; a second step of cutting slopes of the concavo-convex ridges 42 of the corrugate sheet by a pair of second rollers 6 and 6′ having cutting edges 61 and 61′ arranged in an offset arrangement to form an offset portion 43; and a third step of bending the offset portion 43 offset and cut in the second step by a pair of third rollers 7 and 7′ having concavo-convex ridges 71 and 71′ arranged in an offset arrangement on the surface thereof. Consequently, the offset-shaped fins 4 can be produced stably and continuously by roll molding without catch and breakage of the material and the production cost as well as the installation area can be reduced.

In the production method of the offset-shaped fins according to the invention, an offset amount D (see FIG. 5) of the cutting edges in the second step is set to about a sheet thickness so that catch of the cut material into the rollers is approximately the same as the sheet thickness. In this way, the peeling property of the material from the rollers can be improved and catch and breakage of the material can be suppressed.

In the production method of the offset-shaped fins according to the invention, gaps G (see FIG. 6) are disposed between bent teeth offset and arranged in the third step so as to avoid contact of the material with the rollers. Consequently, the peeling property of the material from the rollers can be improved and penetrating and breakage of the material can be suppressed.

In the production method of the offset-shaped fins according to the invention, intermediate rollers 8 for guiding the sheet material under molding are arranged between the first roller 5, 5′ and the second roller 6, 6′ and between the second roller 6, 6′ and the third roller 7, 7′. Accordingly, the intermediate roller 8 guides the sheet material and can limit its movement, and stable roll molding of the offset-shaped fins 4 can be conducted.

According to another aspect of the present invention, there are provided offset-shape fins 4 produced by the production method of offset-shaped fins described above. Consequently, the offset-shaped fins 4 can be produce by roll molding in the same way as press molding.

According to still another aspect of the present invention, there is provided a pitch changing method of offset-shaped fins involving the steps of supplying offset-shaped fins between at least one pair of pitch changing rollers each having a tooth shape formed on an outer periphery thereof and rotating while meshing with the other so that at least one pair of pitch changing rollers clamps the offset-shaped fins between them, allows them to pass through the pitch changing rollers and changes their pitch, wherein each tooth shape of at least one pair of pitch changing rollers is substantially similar to a profile shape of a transverse section of the offset-shaped fins on each roller side in a traveling direction of the offset-shaped pins after the pitch change by one pair of pitch changing rollers.

According to still another aspect of the invention, there is provided a pitch changing apparatus of offset-shaped fins including at least one pair of pitch changing rollers each having a tooth shape formed on an outer periphery thereof and rotating while being meshed with the other so that at least one pair of pitch changing rollers clamps the offset-shaped fins between them, allows them to pass through the pitch changing rollers and changes their pitch, wherein each tooth shape of at least one pair of pitch changing rollers is substantially similar to a profile shape of a transverse section of the offset-shaped fins on each roller side in a traveling direction of the offset-shaped pins after the pitch change by one pair of pitch changing rollers.

According to the construction described above, each tooth shape of at least one pair of pitch changing rollers, in particular, is substantially similar to the profile shape of the transverse section of the offset-shaped fins on each roller side in the traveling direction of the offset-shaped pins after the pitch change by one pair of pitch changing rollers. Therefore, the pitch of the offset-shaped fins can be reliably changed to a predetermined and desired pitch by causing at least one pair of pitch changing rollers to clamp the offset-shaped fins between them, by passing the offset-shaped fins through the pitch changing rollers and by changing their pitch, and the variance of the pitch per crest can be suppressed to minimum. When the pitch changing method and the pitch changing apparatus according to the invention are combined with the production line of the offset-shaped fins by roll molding, the speed of production of the offset-shaped fins having a desired fin pitch and extremely little variance of the fin pitch per crest can be increased, and the production cost, the installation cost, installation area and the energy cost can be drastically reduced.

The present invention may be more fully understood from the description of preferred embodiments of the invention, as set forth below, together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial perspective view of a stacked type heat exchanger;

FIG. 2 is a perspective view of offset-shaped fins;

FIGS. 3A to 3C are explanatory views each for explaining a production method of offset-shaped fins according to an embodiment of the invention, wherein FIG. 3A shows bending of a first step, FIG. 3B shows cutting of an offset portion of a second step and FIG. 3C shows bending of the offset portion of a third step;

FIG. 4 is an enlarged view showing the shape of each roller in the production method of the offset-shaped fins according to the embodiment of the invention;

FIG. 5 is an enlarged view of a cutting edge of a second roller;

FIG. 6 is an enlarged view of a surface structure of a third roller;

FIG. 7 is an explanatory view for explaining a roller arrangement in a production method of offset-shaped fins according to another embodiment of the invention;

FIG. 8 is an explanatory view for explaining the production of fins by press working according to the prior art;

FIG. 9 is an explanatory view for explaining roll molding according to the prior art;

FIGS. 10A to 1OC show the sequence of a production method of offset-shaped fins according to the prior art, wherein FIG. 10A shows cutting and bending of an offset portion as a first roll molding step, Fig. 1OB shows offset molding as a second roll working step and Fig. 1OC shows a joint portion;

FIG. 11A is an image view of offset-shaped fins and FIG. 11B is a transverse sectional view of the offset portion in FIG. 11A;

FIG. 12 is an image view of a pitch changing apparatus for offset-shaped fins having three pairs of pitch changing rollers;

FIG. 13 is an enlarged view of a portion A in FIG. 12; and

FIG. 14 is an image view showing a pitch changing procedure according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A production method of offset-shaped fins according to the present invention and the offset-shaped fins produced by this production method will be explained hereinafter with reference to the accompanying drawings. FIG. 1 shows an example of a stacked type heat exchanger. In the stacked type heat exchanger, a plurality of heat transfer tubes 1 are extended in parallel with one another between a pair of headers not shown, and corrugate fins (outer fins) 2 are arranged between the heat transfer tubes 1. In other words, a heat exchange core portion is formed as the heat transfer tubes 1 and the outer fins 2 are alternately stacked. Consequently, heat exchange is made between a heat exchange medium F1 flowing inside the heat transfer tubes 1 and a heat exchange medium F2 passing through the outer fins 2 outside the heat transfer tubes 1.

In this case, it has been customary to insert and arrange inner fins 3 into the heat transfer tube 1, as shown in FIG. 1, in order to promote the heat exchange. The offset-shaped fins 4 shown in FIG. 2 have been used in the past as the inner fins 3. In the offset-shaped fins 4, a plurality of concavo-convex ridges 4A to 4E that are so shaped as to repeat the concavo-convexities are juxtaposed with one another and the concave-convex ridges (4A, 4B), (4B, 4C), (4C, 4D) and (4D, 4E) adjacent to one another are offset (deviated) in the extending direction of the concavo-convexities. These concavo-convex ridges 4A to 4E are connected to one another at bond portions 41. In other words, the convex portions of these concavo-convex portions 4A to 4B are partially connected to one another while their concave portions are partially connected to one another. It becomes thus possible to make the length of the bond portion 41 greater than the sheet thickness t that had been impossible according to the prior art.

Incidentally, it is also possible to use the offset-shaped fins 4 as the outer fins 2.

Next, a production method of the offset-shaped fins according to this embodiment will be explained. FIGS. 3A to 3C show a process layout when the offset-shaped fins are roll molded and FIG. 4 shows a roller shape in each step. A flat sheet-like material 40A as a material of the offset-shaped fins 4 is continuously supplied as the sheet material 40A is unwound and delivered from the condition where it is wound into a coil shape as shown in FIG. 4. The sheet material 40A is first supplied between a pair of first rollers 5 and 5′ that are arranged at up and down positions and, the first lower roller 5′ turns clockwise and the first upper roller 5 turns counter-clockwise. As shown in a partial enlarged view of FIG. 4, concavo-convex ridges 51 and 51′ are formed on the surface of each first roller 5 and 5′. As the sheet material 40A travels between the first rollers 5 and 5′ meshing with each other, the sheet material 40A is bend-molded into concavo-convex ridges 42 as shown in FIG. 3A to form a corrugation shape sheet 40B. This is the first step of roll molding.

The sheet material 40A processed into the corrugation shape sheet 40B in the first step is subsequently introduced between a pair of second rollers 6 and 6′ that are similarly arranged at up and down positions and the second lower roller 6 turns clockwise and the second upper roller 6 turns counter-clockwise. As shown in a partial enlarged view of FIG. 4, cutting edges 61 and 61′ are formed on the surface of each second roller 6 and 6′, and are arranged in the offset arrangement with each other. As the corrugation shape sheet 40B travels between the second rollers 6 and 6′ meshing with each other, the offset portions 43 on the slope of the concavo-convex ridges 42 in the corrugation shape sheet 40B are cut to form a corrugation shape sheet 40C that is offset and cut as shown in FIG. 3B. This cutting step is the second step of roll molding. FIG. 5 shows the cutting edges 61 and 61′ in further enlargement. In this case, the offset amount D of the cutting edges 61 and 61′ is approximate to the thickness of the sheet material 40A.

The corrugation shape sheet 40C offset and cut in the second step is subsequently introduced between a pair of third rollers 7 and 7′ that are similarly arranged at up and down positions and the third lower roller 7′ turns clockwise and the third upper roller 7 turns counter-clockwise. As shown in a partial enlarged view of FIG. 4, corrugation shapes 71 and 71′ in which the concavo-convex ridges are arranged in the offset arrangement with each other are formed on the surface of each third roller 7, 7′. Therefore, as the offset and cut corrugation shape sheet 40C travels between the third rollers 7 and 7′ meshing with each other, the offset portions 43 are bent and the final offset-shaped fins 4 can be obtained as shown in FIG. 3C. This is the third step of roll molding. FIG. 6 shows the surface of the third rollers 7 and 7′ enlarged. Gaps G are formed between bending teeth of the corrugation shapes 71 and 71′ that are offset arranged, to avoid the contact of the sheet material with the third rollers 7 and 7′. Incidentally, the sheet material after the third step is cut into a predetermined length in the next step into the final offset shape fins 4.

As explained above, in the production method of the offset-shaped fins according to this embodiment, cutting and bending of the offset portions 43 of the corrugation shape sheet 40B are the second and third steps, respectively. Consequently, roll molding can be carried out without penetrating the offset-shape fins 4 into the roller. Because the posture of the concavo-convex bond portions 41 offset does not change (remains flat) and deformation can be suppressed, breakage of the bond portions 41 can be suppressed and stable processing of the offset-shape fins 4 can be conducted. Peeling of the sheet material from the rollers 6 and 7 can be improved and penetrating and breakage of the sheet material can be suppressed by setting the offset amount D of the cutting edges 61 and 61′ to about the sheet thickness and by securing the gaps G between the bending teeth of the corrugation shapes 71 and 71′ that are arranged in the offset arrangement.

In the embodiment described above, the offset-shape fins 4 are produced through the three steps, that is, the first, second and third steps. However, the bending step into the corrugation shape as the first step can be omitted. In this case, bending into the corrugation shape and cutting of the offset portion are simultaneously carried out in the second step described above.

FIG. 7 shows the arrangement of rollers to explain a production method of offset-shaped fins according to another embodiment of the invention. In this embodiment, the first to third steps and the first to third rollers 5, 6 and 7, each forming a pair, are the same as those of the embodiment described above. However, intermediate rollers 8 are interposed between the first roller 5 and the second roller 6 and between the second roller 6 and the third roller 7, respectively. The intermediate rollers 8 guide the sheet materials 40B and 40C during processing and can feed the sheet materials with a suitable tension. Stable processing becomes possible by passing the sheet materials 40B and 40C through the intermediate rollers 8 by restricting the behavior of the sheet materials.

As explained above, as the present invention can produce the offset-shaped fins by roll molding, high speed processing of the offset-shaped fins becomes possible and a processing cost, an installation cost, an installation area and an energy cost can be drastically reduced.

Incidentally, the offset-shaped fins according to the invention can be appropriately used as the inner fins of an oil cooler, as a heat exchanger.

Next, a method for changing the pitch of the offset- shaped fins and an apparatus for the method will be explained with reference to FIGS. 11 to 14. FIG. 11A is an image view of the offset-shaped fins and Fig. 11B is a transverse sectional view of the offset portion shown in FIG. 11A. FIG. 12 is an image view of a pitch changing apparatus for the offset-shaped fins equipped with three pairs of pitch changing rollers. FIG. 13 is an enlarged view of an A portion in FIG. 12. FIG. 14 is an image view showing a pitch changing procedure in the invention.

The offset-shaped fins shown in FIG. 11A are produced by changing the pitch of offset-shaped fins mass-produced in advance at a high speed by a continuous processing by roll molding (hereinafter called “offset-shaped fins 100”) to a desired fin pitch and are fitted to equipment. Therefore, the pitch P of the offset-shaped fins 100 does not consider as a target pitch Po of the final application, but is produced generally and unitarily at a uniform pitch that is convenient for high-speed mass production.

FIG. 12 shows a pitch changing apparatus of the offset-shaped fins having three pairs of pitch-changing rollers. Reference numerals 220 a and 200 b denote a first pair of pitch-changing rollers. Reference numerals 300 a and 300 b denote a second pair of pitch-changing rollers and reference numerals 400 a and 400 b denote a third pair of pitch-changing rollers. Each pair of rollers are driven by driving means, not shown, in such a fashion that the upper roller turns counter-clockwise and the lower roller turns clockwise and the offset-shaped fins supplied from the left side can be fed to the right side. Incidentally, reference numerals 200, 300 and 400 denote the offset-shape fins after the pitch change by the first pair of pitch changing rollers, the second pair of pitch changing rollers and the third pair of pitch changing rollers, respectively.

FIG. 13 is an enlarged view of the A portion in FIG. 12. The offset-shaped fins 100, 200 or 300 are supplied from the left side in the drawing, pass through the respective pair of pitch changing rollers and are subjected to the pitch changing processing of the respective level. Reference numerals 220 a′, 300 a′ and 400 a′ denote teeth shapes of the upper pitch changing rollers 200 a, 300 a and 400 a and reference numerals 220 b′, 300 b′ and 400 b′ denote teeth shapes of the lower pitch changing rollers 200 b, 300 b and 400 b, respectively. These teeth shapes are determined by the pair of pitch changing rollers depending on the pitch P to be changed.

More concretely, each tooth shape of the pair of pitch-changing rollers is shaped into a shape substantially similar to the profile shape of the transverse section of the offset-shaped fin in the traveling direction on the side of each roller after the pitch change by the pair of pitch changing rollers. Here, the term “profile shape of the transverse section of the offset-shaped fin in the traveling direction on the side of each roller” has the following meaning. In the transverse section of the offset portion shown in Fig. 11B, for example, two projections disposed in the offset arrangement are shown projected while overlapping with each other. Of the projected shape, the profile shape on the upper side is the tooth shapes 200 a′, 300 a′ and 400 a′ of the upper rollers and the shape of the profile on the lower side corresponds to the tooth shapes 200 b′, 300 b′ and 400 b′. FIG. 13 shows the state where the upper of upper and lower pitch changing rollers clamp the offset-shaped fins 100, 200 or 300 between them and the fins pass through them. In FIG. 13, upper and lower teeth meshing with one another on the extreme right side clamp the offset-shaped fin into the shape corresponding to the tooth shape. In other words, in this state, the offset-shaped fin is already changed to the-desired pitch P and is outputted with the pitch P changed.

FIG. 14 shows an example of the pitch changing procedure of the present invention. Symbol (1) represents the offset-shaped fin 1 the pitch change of which is to be made. The pitch is 3.0 mm in this case. Symbol (4) represents a final target pitch Po and the pitch is 2.5 mm in this case. Here, to change the pitch of the offset-shaped fin 1 having the pitch of 3.0 mm to the final target pitch Po of 2.5 mm of (4), the pitch change is not directly made to the final target pitch of 2.5 mm but is first reduced to 2.6 mm in (2), is further reduced to 2.3 mm in (3) and is thereafter changed to 2.5 mm of the final target pitch (4).

The reason is as follows. If the direct reduction ratio is too great, the difference between the pitch P of the offset-shaped fin before it is supplied to the pitch changing rollers and the pitch of the offset-shaped fins outputted after reduction, that is, the difference of the tooth pitch between the pair of pitch changing rollers to clamp the fin, is so great that the rollers fail to satisfactorily clamp the offset-shaped fin but crush the fin. Therefore, when the pitch reduction amount is great, the process is preferably carried out, dividedly, as described above. When the fin pitch is lowered below the target pitch and is again returned to the target pitch Po, variance of the fin pitch P resulting from spring-back can be suppressed. These factors also hold true of the case where the fin pitch P is increased.

Turning back to FIG. 12, offset-shaped fins 100 having a pitch of 3.0 mm are supplied from the left side of the drawing and after passing through the first pitch changing processing by the first pair of pitch changing rollers 220 a l and 220i b, the offset-shaped fins 100 are outputted as offset-shaped fins 200 having a pitch P of 2.6 mm. The offset-shaped fins 200 further pass through the second pair of pitch changing rollers 300 a and 300 b and are outputted as offset-shaped fins 300 having a pitch of 2.3 mm. Furthermore, the offset-shaped pins 300 having the pitch of 2.3 mm pass through the third pitch changing processing by the third pair of pitch changing rollers 440 a and 400 b and are outputted as the offset-shaped fins 400 having a target pitch Po of 2.5 mm.

Incidentally, three pairs of pitch changing rollers are not always necessary. To reduce the pitch from a pitch P of 3.0 mm to a pitch P of 2.8 mm, for example, the pitch P may be reduced at a time by using only a pair of pitch changing rollers. In other words, the number of pairs of pitch changing rollers may be selected depending on the pitch P to be changed.

In the present invention having the construction described above, each tooth shape of at least one pair of pitch changing rollers has a shape substantially similar to the profile shape of the sectional shape in the traveling direction of the offset-shaped fins on the roller side after the pitch change by the pair of pitch changing rollers. Therefore, as the offset-shaped fins pass through at least one pair of pitch changing rollers while being clamped between the rollers, the pitch of the offset-shaped fins can be reliably changed to the desired pitch set in advance and variance of the fin pitch for each crest can be reduced to minimum. Eventually, when the pitch changing method and the pitch changing apparatus for the offset-shaped fins according to the present invention are combined with a production line of offset-shape fins by roll molding, the production of the offset-shaped fins having a desired fin pitch and extremely small variance of the fin pitch for each crest can be produced at a high speed by a continuous process, and the production cost, the installation cost and the energy cost can be drastically reduced.

While the invention has been described by reference to specific embodiments chosen for the purposes of illustration, it should be apparent that numerous modifications could be made thereto by those skilled in the art without departing from the basic concept and scope of the invention. 

1. A production method of offset-shaped fins in which a plurality of concavo-convex ridges is so juxtaposed with one another as to repeat concavo-convexities and the positions of adjacent one of said concavo-convex ridges are offset in an extending direction of said concavo-convex ridges, comprising: (1) a first step of bending a flat sheet-like material into a concavo-convex shape by a pair of first rollers having concavo-convex ridges formed on the surface thereof to form a corrugate sheet; (2) a second step of cutting slopes of said concavo-convex ridges of said corrugate sheet by a pair of second rollers having cutting edges arranged in an offset arrangement; and (3) a third step of bending said offset portion offset and cut in said second step by a pair of third rollers having concavo-convex ridges arranged in an offset arrangement on the surface thereof.
 2. A production method of offset-shaped fins according to claim 1, wherein an offset amount D of the cutting edges in said second step is set to about a sheet thickness so that penetrating the cut material into said rollers is approximate the same as the sheet thickness.
 3. A production method of offset-shaped fins according to claim 1, wherein gaps G are disposed between bent teeth offset and arranged in said third step so as to avoid contact of the material with said rollers.
 4. A production method of offset-shaped fins according to claim 1, wherein intermediate rollers for guiding said sheet material under molding are arranged between said first roller and said second roller and between said second roller and said third roller.
 5. Offset-shape fins produced by said production method of offset-shaped fins according to claim
 1. 6. A pitch-changing method of offset-shaped fins involving the steps of supplying offset-shaped fins between at least one pair of pitch-changing rollers each having a tooth shape formed on an outer periphery thereof and rotating while meshing with the other so that said at least one pair of pitch-changing rollers clamp said offset-shaped fins between them, allow them to pass through said pitch-changing rollers and change their pitch, wherein each tooth shape of said at least one pair of pitch-changing rollers is substantially similar to a profile shape of a transverse section of said offset-shaped fins on each roller side in a traveling direction of said offset-shaped pins after the pitch change by said one pair of pitch-changing rollers.
 7. A pitch-changing apparatus of offset-shaped fins including at least one pair of pitch-changing rollers each having a tooth shape formed on an outer periphery thereof and rotating while meshing with the other so that said at least one pair of pitch-changing rollers clamp said offset-shaped fins between them, allow them to pass through said pitch-changing rollers and change their pitch, wherein each tooth shape of said at least one pair of pitch-changing rollers is substantially similar to a profile shape of a transverse section of said offset-shaped fins on each roller side in a traveling direction of said offset-shaped fins after the pitch change by said one pair of pitch-changing rollers. 